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 Post subject: back center backstripe
PostPosted: Fri Dec 08, 2017 10:25 am 
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I am currently about to join a two piece wenge back. I intend to have a chevron backstripe installed. Any thoughts on whether I should sandwich it between the two edges or inlay it after the two pieces are joined? Thanks.

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PostPosted: Fri Dec 08, 2017 11:59 am 
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Not sure it matters but I inlay mine.

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PostPosted: Fri Dec 08, 2017 12:05 pm 
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I would inlay for two reasons.

There is no way of knowing how strong a chevron strip is. Once sandwiched in a back it it will definitely be the weak link.

Also, the strip will not be as thick as your back. That means you should put a fill strip in to make up the difference before the back reinforcement strip is put on. It seems like way to much work to me.

But, I'm sure some have done it with success.

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PostPosted: Fri Dec 08, 2017 12:49 pm 
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That type of back strip is usually inlaid into a routed channel. If you're going to sandwich something like that (assuming it's deep enough to do that) you'll certainly want to use a wide reinforcing cross grain strip inside. It need not be very thick, but it needs to be there.


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PostPosted: Fri Dec 08, 2017 1:13 pm 
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I inlay. I always try to break the joint in the off cuts to see where the weak points are. With bwb fiber purfling on either side of the Center strip it always breaks quite easily along the purfling.

With a solid wood center strip inlaid it’s tough to break. That what I usually do now.

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PostPosted: Sat Dec 09, 2017 8:04 am 
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I use a sandwich for a center inlay in the headstock which can be 1/16 in thick or 1.5.-2mm thick . If the center veneer is thin hand rtr, 2 rabett planes , chisel, and glue. I have done it both ways on the back. I prefer to joint my thicker homemade center strip and glue it to the back . If I have a decorative commercial thin center strip I will use a hand rtr just slightly undersize the depth and width . Then I finesse it with a L and rt hand LN rabett plane. I like fish glue, fast tack and then scrape, sand , and finish. My back reinforcement has the grain running in the same direction as the back . This makes it easy to achieve a 15 ft radius. The cross grain spruce IMHO is a traditional holdover from HHG days when back joints could come apart.


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PostPosted: Sat Dec 09, 2017 8:36 am 
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I have done it both ways - sandwiched between or inlayed. Sandwiching allows you to "grow" the back and build a slightly larger instrument from narrower wood. Between the back strip and wide bindings and purflings you can sometimes "grow" the back as much as 1/2 an inch. When I sandwich it I glue a filler strip behind it so the delicate back strip is supported on a piece of wood that moves in the same fashion as the back.
Inlaying it is less work, and if the back is wide enough for what I am building I usually do that.
In -ALL - cases I use a cross grain spruce (or mahogany) strip across the back seam, whether it has a back strip or not. I know some modern builders don't but I think it adds a lot of strength to the joint with no sonic penalty.


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PostPosted: Tue Dec 12, 2017 9:19 am 
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Clay S. wrote:
... In -ALL - cases I use a cross grain spruce (or mahogany) strip across the back seam, whether it has a back strip or not. I know some modern builders don't but I think it adds a lot of strength to the joint with no sonic penalty.


Yep

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PostPosted: Tue Dec 12, 2017 9:34 am 
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I used to get bent out of shape about making sure I got a full length reinforcement strip from one of the luthier supply houses. I have since started just using soundboard plate cut offs and strategically align the seams so they land underneath the back bracing. This works pretty well. If there is worry about keeping individual pieces straight, what I do is use a piece of aluminum stock about a 1/4" thick and 1" wide x 24" long to keep it straight. I put the back onto a flat working board in the go-bar deck and use go-bars to hold down the aluminum bar in the right location. During glue up you can butt the pieces up against the bar on the one side to keep it all aligned.

I think I saw a video posted here where someone did that and it looked like a good idea.

For the next couple of builds I'm using torrefied bracing. I think I'm going to hate the look of regular spruce reinforcement strip up against the torrefied spruce bracing. Maybe I can get enough off cuts from the plates of the top to do the reinforcement strip. They are dreds so I'm not optimistic! :D

Edited to add: To be clear, I'm notching out the reinforcement strip, NOT the bracing!!

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Last edited by bcombs510 on Tue Dec 12, 2017 5:26 pm, edited 1 time in total.

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PostPosted: Tue Dec 12, 2017 10:06 am 
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It just so happens to be I'm building a wenge guitar now and doing the exact same thing. Like others have mentioned I've done it both ways too. This particular one is going to be inlayed simply because I like to join the back as thick as possible and the inlay strip is much thinner so it would make for an awkward sandwich glue up process.

I have always thought too that the lap joint created by inlaying might make for a better joint but I don't know.


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PostPosted: Tue Dec 12, 2017 3:45 pm 
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Sound board cutoffs are all I've used - heck, that's what I thought you were supposed to do idunno

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PostPosted: Tue Dec 12, 2017 4:57 pm 
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Is this another thread getting confused by the term back strip? The back strip is on the outside and is decorative (or can allow you to "grow the back"). I think the term for the strip on the inside is center reinforcement strip or similar. I've been using soundboard cutoffs to make those too. I recently did one from redwood that looked pretty nice inside the finished guitar.



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PostPosted: Tue Dec 12, 2017 5:24 pm 
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J De Rocher wrote:
Is this another thread getting confused by the term back strip? The back strip is on the outside and is decorative (or can allow you to "grow the back"). I think the term for the strip on the inside is center reinforcement strip or similar. I've been using soundboard cutoffs to make those too. I recently did one from redwood that looked pretty nice inside the finished guitar.


I don't think there is confusion though it is always good to clarify especially for anyone who is new reading this discussion in the future. I think the original question was about the outside strip which lead to comments about the reinforcement strip being even more important when considering the presence and approach to doing the center strip. That lead to discussions of how to make the reinforcement strip.

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PostPosted: Tue Dec 12, 2017 5:25 pm 
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And to clarify... I was saying back strip when I meant reinforcement strip (fixed now :D)

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PostPosted: Tue Dec 12, 2017 6:34 pm 
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bcombs510 wrote:
For the next couple of builds I'm using torrefied bracing. I think I'm going to hate the look of regular spruce reinforcement strip up against the torrefied spruce bracing. Maybe I can get enough off cuts from the plates of the top to do the reinforcement strip. They are dreds so I'm not optimistic! :D



You can darken Spruce in the oven. Start around 300 degrees and pull it out occasionally to compare to your terrified ;) material. Works great for color aging splints too because the color change goes through so you won't scrape/sand it away.

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PostPosted: Tue Dec 12, 2017 6:35 pm 
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Excellent. Thanks, Dave!!


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